My 125 was parked a few years back and not used since then, was running. Bought a new battery and coil, cleaned out the fuel system and carb. Doesn't appear to have any spark, isn't there some about these hydrostatics that won't let spark go to the plug, like making sure the pedal on the left is engaged. Also how to you get a hydro cub to roll freely? Like as if it was in neutral?

The engine turns over really well, it just seems to me that there was something that would not let it start unless it was engaged...haven't had this Cub running in maybe 10 years, having trouble remembering it's unique set up...I have the service manual but not the operators manual.

I will try and add more info as I try and figure it out. Should I replace the ballast resistor? What do they do?

The engine cranks no problem, just no spark, there is a good flow to the carb, too. Thanks Eugene

I am not familiar with the hydros but I believe if the safety switch is still operational the brake needs to be pushed in. Many times these are bypassed as they are a common problem, especially with the gear drives. Wiring can be a challenge on these, suggest doing some tracing as Eugene suggested if the switch isn't the issue. I just experienced the same issue on a 125 and I pulled the plug from the safety switch and put a jumper on it and it fired right up! It was a "scrap yard rescue" that hadn't run in years, had lights, rear weights, a good front blade, rear hitch and IH helper spring.... got it for a song... kept the few things I wanted and gave it to my son in law, he was excited, as was my grandson when he got a ride on it!

Remove the points cover. Open points. Ignition on, check for voltage at the points.

Or, points open, ignition on. Remove coil wire and lay next to block. Jump the points with a flat bladed screw driver. If you get a spark, problem is the points.

Conduct compression tests?

Will check this out and test for compression, although even not used in about 10 years it seems to have good compression and seems to still be solid, this Cadet is totally original and has an original electrical system...thanks

On the 125, there two safety interlocks, and either one will cause the starter interrupt, i.e., nothing will happen when you turn the key, the starter will not turn over. One, the PTO must be disengaged, and two, the clutch/brake pedal must be depressed. If you can get the starter to turn the engine, then the safety switches are ok. There are no other special safety features on a hydro over a gear drive on the older Cadets.

If you are cranking and there's no spark, and especially if it has sat for a long time, the points are corroded and not opening. Take the points cover off (left side of engine, front, bottom, little cover protruding out about 1" x 1" x 2"). Crank the engine and see if you have a nice blue spark at the points. If not, a little sand paper will clean them up.

Getting the tractor to roll freely may be difficult. There is a Hydro Dump lever on the side of the transmission tunnel, right side of the frame. This must be held up while pushing the tractor. If you lift this and there is no resistance, the arms are broken off (VERY COMMON) and you cannot roll the tractor. There is no other disconnect for the hydro on a 125. Later hydro cadets had self dumping transmissions, so they would roll around when turned off. This one does not, so the hydro is always locked. Even with the dump lever held up, if it's working properly, it will NOT roll like in neutral. There is always some drag on the hydro, so it will whine a little and be a little difficult to push around.

Honestly, if it ran when parked, the easiest way to get it going will be to put a new spark plug, new points, and fresh gas in it. Completely drain the tank and put new gas in it. Tap the float bowl on the carb a few times to get the float unstuck. Also, Sea Foam makes a product called Deep Creep. I would take the fuel line off the carb and spray this into the carb fuel inlet. I would also spray this into the air intake of the carb and the spark plug hole while the plug is out. Spray a ton of it in and just let it sit for an hour or two while working on other things. This stuff works miracles on old engines that have sat for a while. Trust me!

Since the "K" series Kohler engines have an automatic compression release, a compression test like you would perform on an ordinary engine, will not be accurate. There is a procedure to check the compression in the service manual.

gitractorman wrote:If you are cranking and there's no spark, and especially if it has sat for a long time, the points are corroded and not opening. Take the points cover off (left side of engine, front, bottom, little cover protruding out about 1" x 1" x 2"). Crank the engine and see if you have a nice blue spark at the points. If not, a little sand paper will clean them up. Bill